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On the base of SD-3 and SPR-3, more perfect models
of universal plotting instruments are being elaborated.
Machines for differential rectification:
Differential photorectifier DFT.- Is intended for
automatic rectification of photographs of highlands
under utilization of previously obtained information.
DFT permits to eliminate the errors on the boundaries
of strips of the orthophotograph as are caused by
height differences of points within elementary areas;
this enabled to triple the width of Strips of the ortho-
photograph. The principle of affine rectification made
use of in this instrument makes it possible to plot
photographs of any focal length. The DFT consists of an
orthoprojector and an automatized control device. The
orthoprojector is a single-picture optical- mechanical
instrument. Introducing of a photograph in the ortho-
projector is fulfilled according to its orientation
elements,as are read on the scales of the analog instru-
ment when plotting a stereopair to which the given
photograph belongs. The orthoprojector is working under
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ch makes use of in-
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guidance of an automatic control whi
formation registered on a perforated tape. This infor-
mation is obtained with the help of an electronic com-
puter from a digital model being plotted on the analog
machine simultaneously with contour drawing.
Orthophotoprojector OFPD.- Is based on the principle of
the SD-5 stereograph. The scale of the orthophotograph
obtained with this instrument is equal to that of the
model. Thanks to its light-tight design, the instrument
may be used in normal light conditions. The magazine may
be loaded either with plates or film. When plotting
photographs, profiling is carried out by hand, i.e.
the stereoscopic image of the mark is made to coincide
with the stereomodel by the aid of & wheel X, connected
in this case with a drive screw.